Foundry composition



2,822,278 FOUNDRY COMPOSITION Harry W. Dietert and William M. Ball III, Detroit, Mich,

assignors, by mesne assignments, to International. Minerals & Chemical Corporation, Chicago, Ill.j

No Drawing. Application September 7, 1951 Serial No. 245,644

5 Claims. (Cl. 106-383) Our invention, relating generally to foundry practice, more particularly concerns a new foundry composition especially adapted for the production of molding sands, molds and cores. Additionally, it concerns foundry molds and cores produced from such compositions.

Among the objects of our invention, therefore, is to provide a new foundry composition of improved, smoothed and finished surface, with high green strength, imparting superior finish to the casting, and itself being highly resistant to penetration by the molten metal, and displaying important advantageous hot strength properties; which composition effectively minimizes likelihood of factory workers contracting silicosis; and which composition is readily and inexpensively formed in certain and predictable manner by known and tried foundry practices, themselves simple, certain, rapid and involving minimum cost elements.

Other objects and advantages of our invention in part will be obvious and in part pointed out hereinafter during the course of the following description, all considered in the light of the claims at the end of this specification.

To facilitate more ready and thorough understanding of our invention it is important to note at this point that the art of casting metal comprises a large part of foundry practice as engaged in today. In casting, the metal is brought in desired convenient manner to molten condition. It is thereupon poured into molds, to produce the resulting casting. It is Well known, however, that important practical problems are encountered in proper molding techniques, problems which become increasingly difficult as the detail of the casting becomes more intricate and involved. It is highly important that the finish detail conform as closely as possible to that of the actual pattern, in this manner minimizing the after-treatment, illustratively grinding, tumbling, and the like, required to bring the finish detail and dimensions of the casting into conformity with that of the pattern. To achieve this, heretofore it has frequently been the practice to add to the molding sand, from which the mold is usually shaped, some element which will smooth the foundry sand and impart to it the ability, not only to produce smooth surface detail, but to retain it both during removal of the pattern from the sand and as well, throughout the entire pouring operation.

It heretofore has frequently been the practice to-employ silica flour as an ingredient of foundry compositions, this substance effectively smoothing the surface of the mold to required extent, and resulting in castings of superior finish. An important objection, however, to the use of silica flour has been that it is a highly effective and active source of silicosis to the plant operators. Accordingly, considerable work and effort has been directed to the'etfective removal of- -this-silicosisg hazard. Until our researches, however,1'no-1e1;itirelysatisfactory method or composition has heretofore been evolved for achieving this objective.

An important object of our invention,-- therefore, is to provide a new foundry'compositiomas well as anew foundry sand embodying the same, particularly adapted for use as a molding sandfinthe production of molds and cores, both of which are readily provided in inexpensive manner, which foundry composition effectively imparts high green strength and high hot strength to the resulting mold, the latter becoming highly resistant to metal penetration and producing smooth, detailed castings, all in the substantial absence of any possible silicosis hazard. In the practice of our invention we use olivine flour in finely divided form; This isa magnesiurnand iron silicate. Olivine is found. inthe natural ate in substantial quantities in the northwestern part of this ountry, and is readily available. 7 e

We find that theadmixture -of about 10% olivine flour to about sand and .4% westernbentonite. (the latter as a binder) produces a composition displaying highly advantageous molding qualities, while avoiding; allsilicosis hazard. Moreover, not only are these prop.--

erties advantageouswhen ,viewedfrom ait-absolute stand-- point, but when compared with generallysirnilar molding; sands but in whichrsilicaflouris incorporated, they are found to be superior theretoin most respects. Illustratively, whereas the green properties of those sands including olivine flour are found to be sustantially identical to those of sands containing silica flour, any difference which was observed was in favor.. of the olivine flour sands. For example, the olivinesanddisplays a slightly greater permeability and, as well, a somewhat higher green compression strength. All in all, however, the close identity between the green properties of the said containing olivine flour and that containing .silica flour are surprising. V, n 7 1 Moreover, in comparing the air-set ofuthe .two sands, we find that the sand to which the olivine flour is added displays somewhat higher strength values. The same is true upon comparing the dry properties of the two sands. And in comparing the hot properties of the two sands, we find that the sand in which we include olivine flour displays somewhat higher compression strength at. substantially all temperatures. Moreover, in comparing hotdeformation at 50 pounds loading per square inch, we find that for all practical purposes the two gnds respond alike with the single exceptionnthat the ,silica; flour-sand has slightly higher hot deformation at 50 pounds loadwhen tested at 2000 F. Generally, however, both. compositions display a low degree of hot deformation at 50 pounds per square inch loading. And this is true when a refractory fine material is added to the sands. Sinter points of the two sands are closely related. For all practical purposes the two sands have expansion characteristics extremely close when subjected to 5 pounds loading. 7

The foregoing advantageous features of our composition are best illustrated in certain test data, fully disclosing the various qualities and properties of the two. Thus, for comparison purposes, two like molding compositions are produced, with the single exception that where silica flour is incorporated in one composition, olivine flour is included in the other. The compositions are best shown in the following Table I;

7 hot strength requirements.

TABLE I Composition Silica Olivine Flour Flour A. F. 8. Sec. Sand Percent- 5.5 Western Bentonlte', Percent- 8 4 85 g Silica Flour, Percent 10 Olivine Flour, Percent 10 Mogul (partly dextrinized starch), Percent 0. 5 0. 5 Moisture, Percent 5.8 5.8

The similarity between the green properties of the two compositions is best illustrated in Table 11:

TABLE H Green properties Silica Olivine Flour Flour Compo- Composition sition Wt. 2" Specim 157. 2 l 157. 7 Density 95.3 95. 6 Permeability 63. 7 60. 2 Green Compression, p. s. 1-.-. 5.17 5.52 Green Deformation, inJin 0. 028 0. 0295 Flowability 79. 2 80. 2

It will be noted from Table II that the actual weights of the specimens are substantially the same and ,thcdensities are nearly alike, and that what difference is observed in the permeability, green compression, green deformation, and fiowability while in green state are all in favor of the olivine flour sand. y

In Tables III and IV the air-set properties and drying properties of the two compositions are disclosed:

It will be seen from Tables III and IV that both the airset compression strength and the dry compression strength of the olivine flour composition are appreciably superior to those of the silica flour composition. Y

Finally, we cometo a consideration of the hot properties of the two compositions. Under the hotproperties we gave study to the hot compression, the total hot deformation, the hot deformation in inches per inch at 50 pounds per square inch'loading, the s'intenpoints, and the expansion under 5 pounds loading. And itlwill be observed, from a close consideration of the data incorporated in the followingTableV, that the hotproperties of the olivine flour compositions bear. favorable comparison with those of the silica flour compositions, and are such as to provide adequate fulfillment of all Silica Olivine Flour Flour Compo- Compositlon sition Hot Compression, p. s. L:

600 F 233. 7 268 203. 7 220.7 561. 3 681. 3 2,000 F- 261. 3 186 2 500 F 21. 0 10. 0 Totai Hot Deformation, in./in.:

500 F 0. 0093 0. 000 1,000 F 0. 0088 0. 0103 1,500 F 0.0173 0.0182 2,000 F 0. 0435 0. 0283 2,500 0. 0277 0.0115 Hot deformation at 50 p. s. 1., in./in.:

0 F 0. 0018 0.0021 1,000 F 0.0015 0.0025 0.0025 0. 0028 0. 0072 0. 0042 2,5003 r Smter A Point, deg. F 2280 2225 Expansion 5# load, in./in.'

Retained strength properties Silica Olivine Flour Flour Compo- Compositlon sition Retained Compression, p. s. i 121. 0 124. 3

In heat shocktests of both the silica flour composition and the olivine flour composition we (@serve the spelling resistance of the two compositions to be quite good.

Thus, in the practice of our invention we produce a new foundry composition which possesses substantially all the desired good qualities of the known silica flour compositions, andrwhich at the same time is produced in economical, effective and proved manner, effectively eliminating substantially all hazard of silicosis, heretofore characteristic of foundry practice.

The new composition can be effectively produced in large batches and stockpiled for subsequent use about the foundry. It can be prepared when desired at a central plant and then stored either at the point of manufacture, or at the particular foundry, all in highly etfective manner. No hazard is involved in storing the sand over prolonged periods, so far as concerns hazard to the workmen about the plant. It maybe stockpiled as a composition to be added as desired to molding sands, or it may be preliminarily admixed with the sands and then stockpiled as a prepared molding sand, at' the will of the plant supervisor. Illustratively, the composition made up for addition to molding sands essentially consists of four parts western bentonite binder and ten parts olivine flour.

Danger of silicosis is substantially suppressed. Castings are produced displaying high finish detail. Since the molten metal cannot readily penetrate the sands, appreciable improvement in finish detail is observed. The high hot strength ensures sound castings of even the heaviest types, and these without detrimental gassy spots. Hot deformation is reduced to such value that no production problem is introduced in this respect. All these, as well as many other highly practical objects and advantages attend upon the practice of our invention.

It is apparent that once the broad aspects of our invention are disclosed, many embodiments thereof, both in the composition and in the resulting sand, will readily suggest themselves to those skilled in the art, all falling within the scope of our invention. Accordingly, we intend the foregoing disclosure to be considered as simply illustrative, and not by way of limitation.

We claim as our invention:

1. A composition for inclusion in molding sands, consisting essentially of approximately four parts western bentonite and ten parts olivine flour.

2. A molding sand for foundry use, consisting essentially of a substantial amount of silica sand, a small quantity of western bentonite binder, and about ten percent olivine flour.

3. A molding sand, having a permeability of at least 60, an air-set compression strength of at least 24 p. s. i. and a dry compression strength of at least 239 p. s. i.

and consisting essentially of approximately 85% silica sand, about 4% western bentonite, about 10% olivine flour, and sufiicient moisture to plasticize the same.

4. A foundry mold consisting essentially of about 85 sand, 10% olivine flour and 4% western bentonite.

5. A foundry core consisting essentially of about 85 sand, 10% olivine flour and 4% western bentonite.

References Cited in the file of this patent UNITED STATES PATENTS 2,256,456 mam Sept. 16,- 1941 2,372,236 Wainer Mar. 21, 1945 2,521,614 Valyi Sept. 5, 1950 FOREIGN PATENTS 570,119 Great Britain July 19, 1945 

2. A MOLDING SAND FOR FOUNDRY, USE, CONSISTING ESSENTIALLY OF A SUBSTANTIAL AMOUNT OF SILICA SAND, A SMALL QUANTITY OF WESTERN BENTONITE BINDER, AND ABOUT TEN PERCENT OLIVINE FLOUR. 